Abstract: The system for automatically balancing a centrifuge in operation comprises a system for selectively displacing a mass of fluid inside at least one hollow horizontal tube (25) incorporated in the rotary arm (20), together with an unbalance measuring circuit (7 to 14) for the rotary arm (20) which may be out of balance.

Abstract: The power supply unit (20) includes an average voltage multiphase supply network (21) with power less than the theoretical power required to feed the high-power electric motor (5) for rotary-driving a centrifuge arm (1), a multiphase step-down transformer (21), a first static device (23) for controlling a multiphase rotating machine, said control device (23) having one multiphase input connected to the secondary of the multiphase transformer (22) and one multiphase output connected to a node (29) with electric linkages, one multiphase rotating machine (27) electrically connected to said node (29), a high-capacity inertia flywheel (28) mechanically coupled to said multiphase rotating machine (27) and output terminals (30) connected to said node (29). The high-power electric motor (5) is connected to the output terminals (30) by means of a second static device (7) for controlling an electric motor.